Image transfer mechanism

ABSTRACT

In one embodiment, a transfer roller is provided, which is driven through idler wheels which are adjustable to selectively vary the frictional force between the idler wheels and the rails upon which they ride. Also, the spacing between the transfer roller and the photoconductive chips is adjustable independently of the frictional force between the idler wheels and rails. In another embodiment, one of the rails is segmented, with the chips providing the remaining portion of the one rail. These rails may be adjusted to vary the frictional force and the spacing of the transfer roller from the chips. Shims may be provided as needed on the photoconductive chips in the rail area.

United States Patent [45 1 Patented Feb. 2, 1971 [73] Assignee Eastman Kodak Company Rochester, N.Y.

a corporation of New Jersey [54] IMAGE TRANSFER MECHANISM 5 Claims, 2 Drawing Figs.

2,300,715 11/1942 Vandercooket al.

2.480,436 8/1949 Benavides H 101/186 2,725,010 11/1955 Vandercook et al. 101/186 3,101,050 8/1963 Schaefer et al. 101/186X 3,277,822 10/l966 Maul et a1 101/269 3,283,711 11/1966 Lew 101/269 Primary ExaminerEdgar S. Burr AttorneysRobert W. Hampton and Gary D. Fields ABSTRACT: In one embodiment, a transfer roller is provided, which is driven through idler wheels which are adjustable to selectively vary the frictional force between the idler wheels and the rails upon which they ride. Also, the spacing between the transfer roller and the photoconductive chips is adjustable independently of the frictional force between the idler wheels and rails. In another embodiment, one of the rails is segmented, with the chips providing the remaining portion of the one rail. These rails may be adjusted to vary the frictional force and the spacing of the transfer roller from the chips. Shims may be provided as needed on the photoconductive chips in the rail area.

1 IMAGE TRANSFER MECHANISM CROSS-REFERENC E TO RELATED APPLICATION An apparatus of this invention may be utilized in the device disclosed in commonly assigned U.S. Pat. application, Ser. No. 741,359, filed Jul. l. I968. entitled "Printing Apparatus" to John S. Pollock.

BACKGROUND OF THE INVENTION I. Field of the Invention This invention relates to a transfer device for the transfer of electrostatic toner images from a photoconductor to a receiver. and more particularly to such a device for transferring images from a plurality of photoconductors onto a single receiver in registry.

2. Description of the Prior Art The problem of registering electrostatic toner images has been largely ignored because in most instances only one image was transferred to each receiver. Most attempts to superimpose a plurality of toner images have been trying to precisely align optical systems for three color separation images with the exposure stations and separate transfer stations to provide exact alignment of electrostatic toner images on a receiver to obtain registry. However, as a practical matter, these methods are not very satisfactory because of the extreme difi'iculty in maintaining all parts in proper alignment at all times. Thus. the need for a way of aligning each photoconductor with the receiver for each transfer of an image is apparent.

This alignment problem is of particular importance in copying color originals. In'the usual electrophotographic process, an originaL'such as a color negative, is broken down into its three color components by the use of beam splitters, filters, etc. as is well known in the art. Color separation images thus formed are then projected on to different photoconductive surfaces to form three separate electrostatic images. These images are each toned with a toner having a color complementary to each color separation image. The toned images are finally transferred in registry to a receiver to form a composite color print. Unless the registration of the toner images is held within very narrow limits, the resulting print will be unsatisfactory.

SUMMARY OF THE INVENTION A rotatable transfer roller is mounted on a carriage and in one embodiment is driven by idler wheels which ride on rails running along a transfer path. The pressure between the idler wheels and the rails is adjustable so that this frictional engagement may be maintained at a sufficient level that no slip will occur between the idler wheel and the rails so that transfer of toner images may be made in registry. In addition, the transfer roller is adjustable independently to vary the spacing of it from the photoconductive chips and to vary the pressure between it and the idler wheels. Thus, the transfer roller can be adjusted up and down to vary the spacing between the transfer roller and the chips without altering the driving pressure.

In an alternative embodiment, the structure is simplified by omitting the idler wheels and providing adjustable rails against which the transfer roller rides to provide the desired frictional force for turning the transfer roller and to adjust the spacing between the transfer roller and the chips. One of the rails is segmented with the photoconductive chips forming a portion of the rail. If necessary, the chips may be shimmed along the rail portion to correspond with the adjustment of the segmented rail.

Additional novel features of this invention will become ap parent from the description which follows, taken in conjunc' tion with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS DESCRIPTION OF THE PREFERRED EMBODIMENTS In an electrophotographic device for making composite prints from a single device, separate photoconductive surfaces are charged and exposed to separate images, such as color separation images. to form corresponding electrostatic imagesthercon. The photoconductors then pass through developing stations which tone the electrostatic images for subsequent transfer to a single receiver in registry to make a composite print.

In accordance with this invention, a transfer roller I0 is rotatably mounted on a shaft II supported in a pair of slots, such as slot I2 of bracket I3, adjustably mounted on frame or carriage I4, as by screws I5. Carriage I4 is mounted on spaced rails 16 running along a transfer path and is driven therealong by timing belt 17. The timing belt is driven by motor 18 through endless belt I9. By this means, the transfer roller is moved past photoconductive chips 20, which are aligned and equally spaced by registration pins 21 so that an electrostatic toner image on each chip may be transferred to a receiver 22 supported by transfer roller 10. Conveniently, chips20 are spaced by the registration pins so that the distance between corresponding points on the respective toner images is equal to the circumference of a circle whose radius is equal to the sum of the radius of the transfer roller and the thickness of the receiver so that the toner image will be transferred to the receiver in registry. Transfer roller 10 is rotated by idler wheels 23 which ride on rails 16 ahead of carriage I4 and engage enlarged bearing surfaces 24 of the transfer roller. These enlarged portions nominally have a radius equal to the sum of the radius of transfer roller I0 plus the thickness of receiver 22.

Conveniently, idler wheels 23 are spring loaded against the rails, as by spring 25, extending from idler wheel shaft 26 to shaft 27 on follower wheel 28, riding on the bottom side of the rail. Springs 25 are strong enough to provide the driving friction necessary between idler wheels 23 and rails 16 so that no slippage occurs during the transfer operation. Conveniently, the transfer roller is biased against idler wheels 23, as by spring 29. Transfer roller I0 may be adjusted up and down to adjust the spacing between it and the chips by means of adjustment screw 15 without varying the pressure between idler wheels 23 and transfer roller I0.

In the alternative embodiment of FIG. 2, a transfer roller 30 is rotatably mounted on a shaft 31 supported on a carriage 32. Carriage 32 is movable along a segmented drive rail 33 and continuous drive rail 34 and is driven therealong by timing belt 35 which is driven through endless belt 36 connected to a suitable motor (not shown). After an electrostatic image on the photoconductive surface of chips 37 is developed, the chips are moved into engagement with registration pins 38 to equally space the chips for transfer of the toner images onto a receiver 39 supported by transfer roller 30. The chips may be held in position, as by electromagnets (not shown). Conveniently, the chips are positioned so that the distance between corresponding points on the toner images is equal to the circumference of a circle whose radius is equal to the sum of the radius of the transfer roller plus the thickness of the receiver so that the same portion of the receiver will come in contact with corresponding portions of the toner images so thatthey are transferred thereto in registry.

Each chip has an enlarged end portion 40 which completes segmented rail 33 when the chips are in the transfer position. The frictional engagement of drive rails 33 and 34 with enlarged bearing surfaces 41 of transfer roller 30 may be varied by vertical adjustment thereof, as by adjustment screws 42, as shown. Also, this adjustment will vary the spacing between the transfer roller and the chips. Enlarged chip end portions 40 may be provided with shims, if necessary, so that the surface thereof is aligned with the surface of segmented rail 33. In addition the juncture between enlarged end portions 40 and rails 33 is along a diagonal to minimize any tendency of transfer roller 30 to jump as it rolls across the juncture and thus prevent smearing of the images.

From the foregoing. the novel features of this invention and the advantages thereof are readily apparent, ln the embodiment of FIG. 1. the idler wheels are adjustable to maintain sufficient driving pressure on the rails to prevent slipping while permitting adjustment of the spacing of the transfer roller independently thereof.

In the embodiment of FIG. 2, adjustable drive rails are provided to a vary the spacing and driving pressure. One rail is segmented with en an enlarged end portion of the photoconductive chips completing this rail when the chips are in image transfer position. These portions may be shimmed if necessary so that the surface thereof will be even with the surface of the rails. Advantageously, the intersection or juncture between the segmented portion of the rails and the enlarged portion of the chips is at an angle to prevent any bumping or jumping of the transfer roller which might adversely affect the integrity of the transferred image.

In both embodiments, distance between corresponding portions of adjacent photoconductive chips is exactly equal to the circumference of a circle having a radius equal to the sum of the radius of the transfer roller and the thickness of the receiver sheet.

The invention has been described in considerable detail with reference to preferred embodiments thereof, it will be understood that variations and modifications can be affected within the spirit and scope of the invention.

We claim:

1. A transfer mechanism for transferring, in registry, electrostatic toner images having corresponding points from a plurality of photoconductive chips to a single receiver, said mechanism comprising:

a plurality of registration means for aligning said chips along a transfer path;

a rotatable transfer roller mounted for rotation about a first axis, having a surface for supporting a receiver and being mounted for movement along said path, the distance between corresponding points on said chips being equal to the circumference of a circle having a radius equal to the sum of the radius of said roller and the thickness of said receiver;

a pair of spaced rails extending along said transfer path;

an idler wheel mounted for rotation about a second axis spaced from said first axis for rolling movement along one of said rails and drivingly engageable with said transfer roller to rotate said transfer roller when said idler wheel and said transfer roller are moved along said transfer path;

means for moving said transfer roller and said idler wheel along said transfer path; and

adjusting means for varying the spacing between said transfer roller and said chips during transfer while maintaining engagement between said idler wheel and said transfer roller and between said idler wheel and said rail.

2. A transfer mechanism, as claimed in claim 1, further including:

first resilient means urging said idler wheel toward said rail;

and

second resilient means urging said transfer roller toward said idler wheel and into frictional engagement therewith.

3. A transfer mechanism for transferring, in registry, electrostatic toner images having corresponding points from a plurality of photoconductive chips, each having a rail portion, to a single receiver, said mechanism comprising:

a plurality of registration means for aligning said chips along a transfer path;

a rotatable transfer roller, having a surface for supporting a receiver and being mounted for movement along said path, the distance between corresponding points on said chips being equal to the circumference of a circle having a radius equal to the sum of the radius of said roller and the thickness of said receiver; and

a pair of spaced rails extending along said transfer path, one

of saidrails being segmented so that said photoconductive chips may be inserted against and withdrawn from said registration means, said rail portions of said photoconductive chips intersecting said segmented rail to form a complete rail when said chips are positioned by said registration means and said transfer roller being movable across said segmented rail during transfer of said toner images from said chips to said receiver.

4. A transfer mechanism, as claimed in claim 3, wherein: said rail portion of each of said photoconductive chips intersects said segmented rail along a diagonal juncture to minimize bouncing of said transfer roller on said segmented rail at said junctures.

5. A transfer mechanism for transferring, in registry, electrostatic toner images having corresponding points from a plurality of photoconductive chips located adjacent one side of a transfer path to a single receiver, said mechanism comprising:

a plurality of registration means on said one side of said transfer path for aligning said chips;

a rotatable transfer roller mounted on a shaft, said transfer roller having a surface for supporting a receiver and being mounted for movement along said path, the distance between corresponding points on said chips being equal to the circumference of a circle having a radius equal to the sum of the radius of said roller and the thickness of said receiver;

a pair of spaced rails extending along said transfer path for rotatably moving said transfer roller along said path to transfer said toner images from said chips to said receiver in registry;

a carriage movable along said spaced rails;

a pair of spaced brackets adjustably mounted on said carriage for varying the spacing between said transfer rollers and said chips during transfer, said shaft extending through and being joumaled in means defining a slot in each of said brackets;

an idler wheel rotatable along each of said rails and engageable with said transfer roller to rotate said roller when said roller is moved along said transfer path;

first resilient means urging said idler wheel toward said rail;

and

second resilient means urging said transfer roller shaft along said slots toward said idler wheel and into frictional engagement therewith. 

2. A transfer mechanism, as claimed in claim 1, further including: first resilient means urging said idler wheel toward said rail; and second resilient means urging said transfer roller toward said idler wheel and into frictional engagement therewith.
 3. A transfer mechanism for transferring, in registry, electrostatic toner images having corresponding points from a plurality of photoconductive chips, each having a rail portion, to a single receiver, said mechanism comprising: a plurality of registration means for aligning said chips along a transfer path; a rotatable transfer roller, having a surface for supporting a receiver and being mounted for movement along said path, the distance between corresponding points on said chips being equal to the circumference of a circle having a radius equal to the sum of the radius of said roller and the thickness of said receiver; and a pair of spaced rails extending along said transfer path, one of said rails being segmented so that said photoconductive chips may be inserted against and withdrawn from said registration means, said rail portions of said photoconductive chips intersecting said segmented rail to form a complete rail when said chips are positioned by said registration means and said transfer roller being movable across said segmented rail during transfer of said toner images from said chips to said receiver.
 4. A transfer mechanism, as claimed in claim 3, wherein: said rail portion of each of said photoconductive chips intersects said segmented rail along a diagonal juncture to minimize bouncing of said transfer roller on said segmented rail at said junctures.
 5. A transfer mechanism for transferring, in registry, electrostatic toner images having corresponding points from a plurality of photoconductive chips located adjacent one side of a transfer path to a single receiver, said mechanism comprising: a plurality of registration means on said one side of said transfer path for aligning said chips; a rotatable transfer roller mounted on a shaft, said transfer roller having a surface for supporting a receiver and being mounted for movement along said path, the distance between corresponding points on said chips being equal to the circumference of a circle having a radius equal to the sum of the radius of said roller and the thickness of said receiver; a pair of spaced rails extending along said transfer path for rotatably moving said transfer roller along said path to transfer said toner images from said chips to said receiver in registry; a carriage movable along said spaced rails; a pair of spaced brackets adjustably mounted on said carriage for varying the spacing between said transfer rollers and said chips during transfer, said shaft extending through and being journaled in means defining a slot in each of said brackets; an idler wheel rotatable along each of said rails and engageable with said transfer roller to rotate said roller when said roller is moved along said transfer path; first resilient means urging said idler wheel toward said rail; and second resilient means urging said transfer roller shaft along said slots toward said idler wheel and into frictional engagement therewith. 